Wheeled upright luggage, including smaller carry-on bags or larger suitcases are well known. FIG. 1 shows a related art upright luggage 10 as it is being moved using a handle 12 on its top surface 13 and a set of wheels 16 attached to its bottom surface 14. Typically, the set of wheels 16 is comprised of two wheels separated by approximately the width of the luggage 10, one near each end of an edge of back surface 15, or of the bottom surface 14, to provide stability during movement of the suitcase. Bumpers 17, together with wheels 16, permit the luggage 10 to stand when not moving.
In such a conventional system, some of the weight of the suitcase, centered at point 18, is borne by the person pulling it. A considerable portion of the weight of the suitcase is located between the set of wheels 16 and the handle 12, therefore the set of wheels 16 do not necessarily bear all the weight during movement. The more tilted the luggage 10, the more weight is shifted to the side of handle 12. This fatigues the user, particularly when the suitcase is pulled on a rougher or less even surface, or over long distances.
U.S. Pat. No. 6,148,971 discloses luggage with front wheels provided on the bottom surface, two auxiliary wheels forward of two main wheels, with the main wheels are provided near the center of the bottom surface of the luggage. However, as shown in FIG. 2 of U.S. Pat. No. 6,148,971, when the person pulling the luggage walks normally, dragging the suitcase behind, the auxiliary wheels would typically be of no use, since they do not touch the ground between the main wheels and the handle. U.S. Pat. No. 7,011,195 shows a single auxiliary wheel, similar to that of U.S. Pat. No. 6,148,971, with a different handle, and an even greater loss of payload space inside the suitcase because of the V-shaped design of the bottom surface of the suitcase. Further, U.S. Pat. No. 6,129,365 discloses in FIG. 10 two pairs of wheels on the bottom surface of a suitcase. However, this arrangement requires the person pulling the suitcase to maintain the suitcase in a perfectly upright position substantially 90° to the ground. Also, moving the luggage in such an arrangement makes it difficult to walk in a normal fashion because there is insufficient clearance for the movement of the legs in a normal gait. The complete disclosures of the aforementioned U.S. patents are incorporated herein for all purposes by their reference.
Moreover, when the suitcase is in such a standing position suitable for pulling the suitcase, it is difficult, particularly in the case of a larger suitcase or of an elderly or frail person operating the suitcase, to open the suitcase and view its contents without squatting on the floor alongside the suitcase. Also, packing or unpacking the contents of the suitcase requires the use of a table, bed, stool or other such structure, on top of which the suitcase must be lifted and placed. A suitcase, and suitcase undercarriage system that overcomes these problems would be advantageous.